1. Field of the Invention
This invention relates to a hose, in particular a rubber hose for conveying fuels which is used for connecting metal pipes in the automobile engine room.
2. Description of the Prior Art
Rubber hoses 4 so far used for conveying fuels has, as shown in FIG. 2 in the accompanying drawing, a three-layer structure, namely an inner tube rubber layer 1, a reinforcing textile layer 2 and a weatherresistant outer tube rubber layer 3. In connecting two metal pipes 5, as shown in FIG. 3, both ends of such a hose are respectively put on terminal portions of the pipes 5 in the telescopic manner and then fastened by means of fastener bands 6. However, as a result of recent remarkable technological advances in the automobile industry, in particular increases in fuel pressure and temperature as exhaust emission control measures, the engine room inside is exposed to a very wide range of temperature changes, from a temperature as high as 100.degree. C. to a temperature as low as -40.degree. C. Moreover, gasoline undergoes oxidation and circulates as sour gasoline (gasoline containing peroxides as a result of oxidation at high temperatures). For these and other reasons, automobile fuel hoses are required to have such performance characteristics as would render themselves usable even under severer conditions than before. Under these circumstances, conventional rubber hoses whose inner tube rubber layer is made of a gasoline-resistant general-purpose polymer are no longer usable. Furthermore, gasoline is a limited resource and will anticipatedly be in short supply in the future and therefore attempts are being, made to use a gasoline-alcohol mixture as a fuel to cope with the future situation. Thus it becomes necessary to provide an inner tube rubber layer which is resistant to alcohols highly erosive to rubbers. From these viewpoints, there may be mentioned fluororubbers (also known under the name "FKM") as materials which are satisfactory as far as the performance characteristics mentioned above are concerned. Said fluororubbers have good resistance to heat, sour gasoline, etc. On the other hand, however, their low-temperature characteristics are unsatisfactory and they are subject to cracking due to amine-type additives contained in gasoline. Moreover, they are expensive. Therefore, a measure currently taken comprises forming the inner tube rubber layer, which is internal to the outer tube rubber layer, as a double layer, the inside layer of which is a thin layer of a fluororubber and the outside layer of which is made of a rubber having good low-temperature characteristics, namely a hydrin rubber or an acrylonitrile-butadiene rubber (hereinafter abbreviated as NBR). Nevertheless, the product hoses are still unsatisfactory with respect to costs and amine-caused degradation. They are unsatisfactory in interlayer adhesion between the outside NBR layer and the inside fluororubber layer of the inner tube rubber layer.
Meanwhile, polymer blends composed of an acryl rubber and a fluororesin have been developed as materials which are comparable in sour gasoline resistance and other performance characteristics to the above-mentioned fluororubbers and are fairly inexpensive as compared with the fluororubbers. However, since they are blends, the hardness after curing is high. Thus, hoses manufactured by using them will have insufficient flexibility. Accordingly, rubber hoses which are inexpensive, have all the performance characteristics required of rubber hoses for conveying fuels and, in addition, have good low-temperature characteristics should desirably be provided.
It is an object of the invention, which has been completed under these circumstances, to provide hoses which are inexpensive, are excellent in performance characteristics, such as heat resistance, gasoline resistance, sour gasoline resistance and low-temperature characteristics, and furthermore have good flexibility and durability.